As long as the microphone is connected via USB when you launch Dirac. You would then select the Microphone during setup of Dirac during the “microphone” section. From there you will need to load the FRD text file for the calibration mic from the manufacturer.
The microphone calibration file is a text file that should contain the microphone magnitude response. The file format which is supported by Dirac Live™ consists of lines of <frequency, level> pairs, where the level is given in decibels (dB).
See screenshot below (click to enlarge)